Multilayer vessel



"Nov.2s,144.' Mel JA PER 2,363,967

MULTILAYER VESSEL Filed llay 2, '1942 Thaings McI. can Jasper Arroaunc I UNITED, STATE.

than

Patented Nov.28 1944 I MULTILAYER VESSEL Thomas McLean Jasper, Milwaukee, Wis., as-

' slgnor'to A. ,0. Smith Corporation, Milwaukee,

Wis. a corporation of New York Application May 2, 1942, Serial No. 441,520

' .2 Claims. ((31. 220-3) mine the stress at any given location in the thickness of the wall is known as. the Lam formul and may be stated as follows:

iUh (Rz-- 1) in which:

8 denotes the circumferential tensile stress in pounds per square inch at any given point in the section; I

P denotes the internal fluid pressureiin pounds per square inch on the inside of 'the cylinder;

R denotes the radius in' inches at the point of stress;

R1 denotes the inside radius of the section in inches; and I R: denotes the outside radius of the section in inches. 1

The same general formula may be expected to apply to multi-layer pressure vessels. where the layers are, not placed under a 'prestre'ssed condition. Such vessels have been constructed under the United States patent to R. Stresau,.No. 1 1,925,118. Various methods offabricating such.

greater stren th than A multi-layer cylinder for pressure vessels embodying the invention is illustrated in the accompanying drawing in which the single figure is a perspective'view of such a cylinder. -The cylinder is fabricated by the method described in the Stresau patent referred to above,

by first rolling and welding the inner sheet of metal, and thereafter applying and welding subsequent sheets of metal successively to provide a vessel of many layers tightly fitting upon one another so that the load applied to the inner layer from internal fluid pressure in service will be efflciently transferred and spread between the several layers. The sheets of metal should be sufilciently thin for the diameter of the shell to avoidthe characteristicsof a rigid single plate heavy wall'construction. In practice, for vessels having an inside diameter of about three feet,

the layers or sheets are preferably about onequarter or ilve-sixteenths of an inch thick. The

layers need not all be of the same thickness. One

or more layers may be substantially thicker than the rest. 1

In carrying out the invention the first few layers I, 'say up to about one-third of the thicknes of I the vessel wall; are constructed of a high strength metal such as a low alloy steel or of cold rolled or heat treated steel. The balance of the layers of metal may be constructed of ordinary steel, or,

- '1 as illustrated'in the drawing, may be divided and the next group of layers 2 be constructed of a 1 medium. strength steel and they outer group of layers {constructed of a relatively low strength vesselshave been proposed for prestressing the layers of the vessels in a manner tending to compensate for this unequal rate of stressing in service. a

The-principal object of the present invention is to provide a multi-layer vessel construction which substantially compensates forfthe. stress diife'rential referred to and which "does not need- 1 'to have the steel initially stressed. This enables the'full'strength ofeach sheet ortne steel to beutilized in computing the working pressure.

Another object is to provide a stronger and lighter-weight inulti-layer pressure. vessel.

In carrying out theinvention, the inner layers I of .the vesselareconstructed oi stronger metal but preferably it ls'obtained by' steel.

about 100,000 lbs.- per square inch, the layersof group 2 be constructed of a steel having a ministrength r about 0,000 lbs. per square inch; and-the layers of group 3 be construct'ed of a steehhavinga tensile ,strength'of about 60,000-lbs. per square inch.

Such a vessel will when loaded in service have its several layers stressed more nearly in proportion' to the yield point of the metal "of the several layers'and. eiliciency will be obtained.

7 For thediflerent strengths '50 I the outer layers. This-greaterstrengthlin theinner layers may be obtained .by cold working or heat treating low alloy steel sheets .ofythe several-ilayers will furnish protection animt'the ofstress increase unu metal for each me e;

the steel of the outer layers.

As an illustration of the invention it is sug-' ation in strengt h-being gradual from a maximum i'nthe inner layer to a minimum in the outer layer. However, such a vessel would be relatively Y costly, and for all practical purposes a vessel such as that illustrated having two or three difl'erent strengths of metal is entirely satisfactory. ,With extremely thick-walled vessels of many layers, it maybe practical and of advantage to employ a larger number of groups of layers of different strengths. l

The several layers are stressed more nearly according to the factor of safety to which the vessel is designed and there is less danger of any of the layers being overloaded in service. strength. of the several layers provide the desired factor of safety while withstanding the internal working pressures.

Various embodiments of the invention may be employed within the scope of the accompanying claims.

The invention is claimed as follows: i. A multi-layer high pressure cylindrical shell 'of the class described having a diameter to wall thickness ratio less than about ten, comprising many superimposed cylindrical layers of metal of uniform thickness, substantially free of pre-stress The full and disposed concentrically one within another in tight pressure contact with one another throughout at all times, the inner layers of the shell being composed of metal of higher strength than that of the outer layers to compensate for the difference in rate of stress increase in the several layers when internal fluid pressure is applied to the shell.

2. A multi-layer high pressure cylindrical shell,

of the class described having a diameter to wall thickness ratio less than about ten, comprising many superimposed cylindrical layers of metal of uniform thickness, substantially free of prestress and disposed concentrically one within another in tight pressure contact with one another throughout at all timessaid layers of metal being composed of at least three 'groups, the inner groups of layers being of metal of greater 

